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PM3 Parametric Model

PM3 Parametrized Model 3. PM3 is a version of the AMI method reparametrized by J.J. Stewart. On the whole PM3 gives better estimates of the heat of formation than AMI. [Pg.761]

PM3 Parametric Model 3 reparametrization of MNDO with a core-core repulsion term similar to those of AMl. ... [Pg.286]

Semiempirical methods that also include the a electrons have been developed and are referred to as INDO and CNDO. NDO stands for Neglect of Differential Overlap. We will not treat these approximations here. C in CNDO stands for Complete and I in INDO stands for Intermediate. Approximations where /S is added at the end mean that the parametrization is relevant for the description of excited states and that Cl is used. AMI (Austin model 1) and PM3 (Parametrized model 3) are more recent models that build on the NDO approximation and are still in use. The AMI (developed by M. J. S. Dewar) and PM3 (developed by J. J. P. Stewart) methods are useful to get quick results on comparatively large systems. PM3 in particular has been extensively used in this book, mainly for illustration purposes. [Pg.105]

The methods of the NDDO family were further developed, which resulted in two quite successful parametrizations for organic species [68,69] known as the Austin Model (AMI) and Parametrized Model (PM3) and further, PM5 and SAMI (semi-ab initio model) parametrizations [74,75]. [Pg.119]

As an alternative to ab initio methods, the semi-empirical quantum-chemical methods are fast and applicable for the calculation of molecular descriptors of long series of structurally complex and large molecules. Most of these methods have been developed within the mathematical framework of the molecular orbital theory (SCF MO), but use a number of simplifications and approximations in the computational procedure that reduce dramatically the computer time [6]. The most popular semi-empirical methods are Austin Model 1 (AMI) [7] and Parametric Model 3 (PM3) [8]. The results produced by different semi-empirical methods are generally not comparable, but they often do reproduce similar trends. For example, the electronic net charges calculated by the AMI, MNDO (modified neglect of diatomic overlap), and INDO (intermediate neglect of diatomic overlap) methods were found to be quite different in their absolute values, but were consistent in their trends. Intermediate between the ab initio and semi-empirical methods in terms of the demand in computational resources are algorithms based on density functional theory (DFT) [9]. [Pg.642]

In the late 1960s and early 1970s, Dewar and co-workers developed the modified INDO (MINDO) methods. In 1976, the modified neglect of diatomic overlap (MNDO) method " was introduced. Further refinements were made to MNDO and improved parametrizations, AMI Austin model 7) PM3 parametric method and PM5 parametric method 5), ... [Pg.468]

SMI [50], SMla [50], SM2 [52], SM2.1 [54], SM2.2 [55], SMS [52,56], and SM3.1 [54] methods were parametrized only for water, and the partial charges for the electrostatic contribution were based on a Mulliken analysis of the semiempirical molecular orbital wave functions, in particular the wave functions obtained by the Austin Model 1 (AMI) [57] and the Parametrized Model 3 (PM3) [58]. These charges, like those calculated from ab initio minimum-basis-set Hartree-Fock calculations, tend to overestimate the charge separations and polarities. Since the errors are systematic, the parametric expressions for surface tensions compensate these errors. [Pg.176]

PM3/MM Parametric model 3/molecular mechanical. PM3 is a semiempirical Hamiltonian. Best method for hydrogen bonding, therefore, this is the most versatile method. (Refs. 41, 42) Depends on system 3 to 5 kcal mol ... [Pg.2334]

Cramer C j and D G Truhlar 1992. AM1-SM2 and PM3-SM3 Parametrized SCF Solvation Models for Free Energies in Aqueous Solution. Journal of Computer-Aided Molecular Design 6 629-666. [Pg.650]

Various parameterizations of NDDO have been proposed. Among these are modified neglect of diatomic overlap (MNDO),152 Austin Model 1 (AMI),153 and parametric method number 3 (PM3),154 all of which often perform better than those based on INDO. The parameterizations in these methods are based on atomic and molecular data. All three methods include only valence s and p functions, which are taken as Slater-type orbitals. The difference in the methods is in how the core-core repulsions are treated. These methods involve at least 12 parameters per atom, of which some are obtained from experimental data and others by fitting to experimental data. The AMI, MNDO, and PM3 methods have been focused on ground state properties such as enthalpies of formation and geometries. One of the limitations of these methods is that they can be used only with molecules that have s and p valence electrons, although MNDO has been extended to d electrons, as mentioned below. [Pg.183]

Abstract Quantitative structure-activity relationship (QSAR) analysis for minimum inhibitory concentration (MIC) of phenothiazines and benzo[a]phenothiazines was investigated based on the theoretical calculations. Four different dipole moments (/jq, /xesp g, /zw, and /zesp-w) and heats of formation (AHf) of the phenothiazines [1-20], benzo [n]phenothiazines [21-29], and benz[c]acridines [30-41] were separately calculated in the gas-phase and the water-solution by the conductor-like screening model/parametric method 3 (COSMO/PM3) technique. The MIC values of phenothiazines [1-20] were well correlated to A AHf, HOMO energy and hq. QSAR may be applicable to predict the MIC of phenothiazines. [Pg.253]


See other pages where PM3 Parametric Model is mentioned: [Pg.381]    [Pg.437]    [Pg.47]    [Pg.375]    [Pg.381]    [Pg.437]    [Pg.47]    [Pg.375]    [Pg.1014]    [Pg.369]    [Pg.319]    [Pg.433]    [Pg.1481]    [Pg.95]    [Pg.193]    [Pg.735]    [Pg.281]    [Pg.263]    [Pg.286]    [Pg.162]    [Pg.41]    [Pg.48]    [Pg.388]    [Pg.203]    [Pg.127]    [Pg.2554]    [Pg.158]    [Pg.88]    [Pg.174]    [Pg.379]    [Pg.123]    [Pg.25]    [Pg.52]    [Pg.88]    [Pg.56]    [Pg.10]    [Pg.71]   
See also in sourсe #XX -- [ Pg.3 , Pg.220 , Pg.236 , Pg.246 ]




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